7Be content and its seasonal variation in the ground air around Hangzhou area

Twice investigations around Hangzhou area show that ~7Be content average in the ground air is 5.9mBq.m-3. The content of 7Be is the highest in autumn-winter period reaching about 7.7mBq-m-3; the next is in spring about 6.2mBq.m-3: then is in the early summer about 5.7mBq.m-3, close to the annual average level; and the lowest in a year is in summer-autumn period with a value about 3.8mBq.m-3. Exhibited is a decreasing trend from autumn-winter period to summer-autumn of the next year, which is negatively correlated with the variation of the seasonal rainfall in Hangzhou area. But this trend is different from that reported by UNSCEAR: it is the highest in spring and the lowest in the late autumn. which is based only on 7Bn falling down from the stratosphere. However. the present investigation shows that the seasonal rainfall is the main factor influencing the variation trend of 7Be content in the air.